U.S. patent application number 14/397996 was filed with the patent office on 2015-06-04 for image capturing apparatus and focusing method thereof.
This patent application is currently assigned to HAMAMATSU PHOTONICS K.K.. The applicant listed for this patent is HAMAMATSU PHOTONICS K.K.. Invention is credited to Hideshi Oishi.
Application Number | 20150156397 14/397996 |
Document ID | / |
Family ID | 51209207 |
Filed Date | 2015-06-04 |
United States Patent
Application |
20150156397 |
Kind Code |
A1 |
Oishi; Hideshi |
June 4, 2015 |
IMAGE CAPTURING APPARATUS AND FOCUSING METHOD THEREOF
Abstract
In the image capturing apparatus, the optical path difference
producing member is disposed on the second optical path. Thereby,
the amount of light on imaging an optical image which is focused at
the front of an optical image made incident into the first imaging
device (front focus) and an optical image which is focused at the
rear thereof (rear focus) by the second imaging device can be
suppressed to secure the amount of light on image pickup by the
first imaging device. Further, in the image capturing apparatus,
the first imaging region and the second imaging region on the
imaging area of the second imaging device are positioned on the
front side of the imaging area in a scanning direction of the
sample with respect to the region into which an optical image is
made incident which is conjugate to the first optical image made
incident into the first imaging device. Thereby, it is possible to
obtain in advance a deviation direction of a focus position of the
objective lens by a simple constitution.
Inventors: |
Oishi; Hideshi;
(Hamamatsu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HAMAMATSU PHOTONICS K.K. |
Hamamatsu-shi, Shizuoka |
|
JP |
|
|
Assignee: |
HAMAMATSU PHOTONICS K.K.
Hamamatsu-shi, Shizuoka
JP
|
Family ID: |
51209207 |
Appl. No.: |
14/397996 |
Filed: |
January 17, 2013 |
PCT Filed: |
January 17, 2013 |
PCT NO: |
PCT/JP2013/050857 |
371 Date: |
October 30, 2014 |
Current U.S.
Class: |
348/79 |
Current CPC
Class: |
G02B 21/241 20130101;
G02B 21/02 20130101; H04N 5/23212 20130101; G02B 7/343
20130101 |
International
Class: |
H04N 5/232 20060101
H04N005/232; G02B 21/02 20060101 G02B021/02 |
Claims
1-12. (canceled)
13. An apparatus for capturing an image of a sample, the apparatus
comprising: a stage configured to support the sample; a stage
control unit configured to move the stage at a moving speed; an
objective lens configured to face to the sample; a light dividing
unit configured to divide an optical image of at least a portion of
the sample into a first optical image and a second optical image; a
first imaging unit configured to capture at least a portion of the
first optical image; a second imaging unit configured to capture at
least a portion of the second optical image and provide image data;
a focus control unit configured to analyze the image data to
control a focus position of the objective lens based on the
analysis result; a region control unit configured to set a first
imaging region and a second imaging region for capturing the at
least the portion of the second optical image on an imaging area of
the second imaging unit; and an optical path difference producing
member configured to give an optical path difference to the second
optical image; wherein the region control unit sets the first
imaging region and the second imaging region so as to be positioned
on the front side of the imaging area in a scanning direction of
the sample with respect to a region into which an optical image is
made incident which is conjugate to the first optical image made
incident into the first imaging unit.
14. The apparatus of claim 13, wherein the optical path difference
producing member is a flat plate member which is disposed so as to
overlap at least on a part of the imaging area, and the region
control unit sets the first imaging region and the second imaging
region respectively at a region which will overlap on the flat
plate member and a region which will not overlap on the flat plate
member so as to avoid a shadow of the second optical image by an
edge part of the flat plate member.
15. The apparatus of claim 13, wherein the optical path difference
producing member is a member having a part which continuously
changes in thickness along the in-plane direction of the imaging
area, and the region control unit sets the first imaging region and
the second imaging region so as to overlap on a part of the optical
path difference producing member which is different in
thickness.
16. The apparatus of claim 13, further comprising; an objective
lens control unit configured to control a position of the objective
lens relatively with respect to the sample based on control by the
focus control unit, wherein the objective lens control unit will
not actuate the objective lens during analysis of the focus
position which is being performed by the focus control unit and
will allow the objective lens to move with respect to the sample in
one direction during analysis of the focus position which is not
being performed by the focus control unit.
17. The apparatus of claim 13, wherein the region control unit sets
the position of the first imaging region and the position of the
second imaging region in such a manner that an interval between a
region into which an optical image is made incident which is
conjugate to the first optical image made incident into the first
imaging device and the first imaging region is different from an
interval between the region into which an optical image is made
incident which is conjugate to the first optical image made
incident into the first imaging device and the second imaging
region.
18. The apparatus of claim 13, wherein the region control unit sets
waiting time from image pickup at the first imaging region to image
pickup at the second imaging region based on a scanning speed of
the stage and a distance between the first imaging region and the
second imaging region.
19. A method of capturing an image of a sample, the method
comprising: by an objective lens, acquiring an optical image of at
least a portion of a sample supported on a stage; moving the stage
at a moving speed; dividing the optical image into a first optical
image and a second optical image; by a first imaging unit,
capturing at least a portion of the first optical image; by a
second imaging unit, capturing at least a portion of the second
optical image given an optical path difference and providing image
data; analyzing the image data so as to control a focus position of
the objective lens based on the analysis result in an analysis
period, wherein a second imaging unit is set so as to capture an
optical image which is on the front side in a scanning direction
with respect to the portion of the first optical image.
20. The method of claim 19, wherein the second optical image is
given continuously the optical path difference.
21. The method of claim 19, wherein by an optical path difference
producing member, which has a part continuously changing in
thickness along the in-plane direction of the imaging area, giving
the optical path difference.
22. The method of claim 19, further comprising: controlling a
position of the objective lens relatively with respect to the
sample based on the analysis result in a control period; wherein
the analysis period and the control period happen alternately.
23. The method of claim 19, wherein the step of capturing the at
least the portion of the second optical image is at least twice in
one of the analysis.
24. An image capturing apparatus, comprising: a stage configured to
support a sample; a stage control unit configured to move the stage
at a moving speed; an objective lens configured to face to the
sample; a light dividing unit configured to divide a optical image
of at least a portion of the sample into a first optical image and
a second optical image; a first imaging unit configured to capture
at least a portion of the first optical image; a second imaging
unit configured to capture at least a portion of the second optical
image and provide image data; a focus control unit configured to
analyze the image data to control a focus position of the objective
lens based on the analysis result, wherein a second imaging unit is
set so as to capture an optical image which is on the front side in
a scanning direction with respect to the portion of the first
optical image.
25. An image capturing apparatus, comprising: a stage configured to
support a sample; a stage control unit configured to move the stage
at a moving speed; an objective lens configured to face to the
sample; a light dividing unit configured to divide a optical image
of at least a portion of the sample into a first optical image and
a second optical image; a first imaging unit configured to capture
at least a portion of the first optical image; a second imaging
unit configured to capture at least a portion of the second optical
image and provide image data; a focus control unit configured to
analyze the image data to control a focus position of the objective
lens based on the analysis result, wherein the stage control unit
that controls the stage such that each portions of the one or more
optical images are received by the second imaging unit prior to it
being received by the first imaging unit.
26. A method of capturing an image of a sample, the method
comprising: by an objective lens, acquiring an optical image of at
least a portion of a sample supported on a stage; moving the stage
at a moving speed; dividing the optical image into a first optical
image and a second optical image; by a first imaging unit,
capturing at least a portion of the first optical image; by a
second imaging unit, capturing at least a portion of the second
optical image given an optical path difference and providing image
data; analyzing the image data so as to control a focus position of
the objective lens based on the analysis result in an analysis
period, wherein controlling the stage such that each portions of
the one or more optical images are received by the second imaging
unit prior to it being received by the first imaging unit.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image capturing
apparatus which is used for capturing images of a sample, etc., and
also relates to a focusing method thereof.
BACKGROUND ART
[0002] Image capturing apparatuses include a virtual microscope
apparatus in which, for example, an imaging region of a sample is
in advance divided into a plurality of regions to image the divided
regions at a high magnification and, thereafter, to synthesize the
regions. In capturing images by using the virtual microscope as
described above, conventionally, as conditions for picking up
images of a sample such as a biological sample, a focus map which
covers an entire region of the sample is set to capture images of
the sample, while focus control is performed based on the focus
map.
[0003] In preparation of the focus map, at first, an image
capturing apparatus equipped with a macro optical system is used to
capture an entire sample as a macro image. Next, the thus captured
macro image is used to set an image pickup range of the sample and
also the range is divided into a plurality of regions to set a
focus obtaining position for each of the divided regions. After the
focus obtaining position has been set, the sample is transferred to
the image capturing apparatus equipped with a micro optical system
to obtain a focus position at the thus set focus obtaining
position, thereby preparing a focus map with reference to the focus
position.
[0004] However, in preparation of the above-described focus maps,
there has been a problem that processing needs time. Further,
suppression of intervals and the number of focuses to be obtained
would reduce the time necessary for the processing. In this case,
however, there has been a problem of reduction in focus accuracy.
Therefore, development of dynamic focus for capturing images of a
sample at a high magnification, with a focus position being
obtained, is now underway. The dynamic focus is a method in which a
present direction of the focus position deviating from the height
of an objective lens is detected based on a difference in light
intensity or a difference in contrast between an optical image
which is focused at the front of an optical image made incident
into an imaging device for capturing an image (front focus) and an
optical image which is focused at the rear thereof (rear focus),
thereby allowing the objective lens to move in a direction at which
the deviation is cancelled to capture an image.
[0005] A microscope system disclosed, for example, in Patent
Document 1, is provided with a second imaging unit which images a
region at the front of a region imaged by a first imaging unit, an
automatic focusing control unit which adjusts a focusing position
of an objective lens at an imaging position of the first imaging
unit based on an image picked up by the second imaging unit, and a
timing control unit which synchronizes timing at which a divided
region moves from an imaging position of the second imaging unit to
the imaging position of the first imaging unit with timing at which
an image forming position of the divided region imaged by the
second imaging unit is positioned at an imaging area of the first
imaging unit depending on a distance between the divided regions
and a speed at which a sample moves. Further, in a microscope
apparatus disclosed, for example, in Patent Document 2 or Patent
Document 3, a glass member is used to make a difference in optical
path length inside a light guiding optical system for focus
control.
CITATION LIST
Patent Literature
[0006] [Patent Document 1] Japanese Patent Application Laid-Open
No. 2011-081211
[0007] [Patent Document 2] Japanese Patent Publication No.
WO2005/114287
[0008] [Patent Document 3] Japanese Patent Publication No.
WO2005/114293
SUMMARY OF INVENTION
Technical Problem
[0009] In the microscope system described in Patent Document 1, a
half mirror and a mirror are used to form an optical path
difference optical system, by which light different in optical path
length is made incident into each of two imaging regions of the
second imaging unit. In the conventional microscope system, for
example, a line sensor is used to constitute a first imaging unit
and a second imaging unit. In the line sensor, it is important to
secure an amount of light for capturing a clear image due to short
exposure time. However, in the conventional microscope system,
light is divided by the optical path difference optical system.
Thus, there is posed such a problem that it is difficult to secure
an amount of light.
[0010] Further, in the conventional microscope system, an optical
surface of an optical path dividing unit is inclined, and a region
imaged by the second imaging unit is adjusted so as to be
positioned on the front side of a region imaged by the first
imaging unit in a scanning direction of a sample, thereby obtaining
in advance a deviation direction of a focus position. However, the
above-described constitution poses such a problem that it is
difficult to adjust the optical surface. The half mirror and the
mirror are used to constitute the optical path difference optical
system. Thus, such a problem is also posed that light which has
passed through the optical path difference optical system is less
likely to gather on the imaging area of the second imaging
unit.
[0011] The present invention has been made for solving the
above-described problems, an object of which is to provide an image
capturing apparatus which is capable of obtaining a deviation
direction of a focus position in advance by a simple constitution
to detect the focus position of a sample at high accuracy and also
to provide a focusing method thereof.
Solution to Problem
[0012] In order to solve the above-described problems, the image
capturing apparatus of the present invention is characterized in
having a stage in which a sample is placed, a stage control unit
which scans the stage at a predetermined speed, a light source
which radiates light to the sample, a light guiding optical system
including a light dividing unit which divides an optical image of
the sample into a first optical path for capturing an image and a
second optical path for focus control, a first imaging unit which
captures a first image by a first optical image divided into the
first optical path, a second imaging unit which is capable of
capturing a two-dimensional image of a second image by a second
optical image divided into the second optical path, a focus control
unit which analyzes the second image to control a focus position of
image pickup by the first imaging unit based on the analysis
result, a region control unit which sets a first imaging region and
a second imaging region for capturing a partial image of the second
optical image on an imaging area of the second imaging unit, and an
optical path difference producing member which is disposed on the
second optical path and gives an optical path difference to the
second optical image along an in-plane direction of the imaging
area, in which the region control unit sets the first imaging
region and the second imaging region so as to be positioned on the
front side of the imaging area in a scanning direction of the
sample with respect to a region into which an optical image is made
incident which is conjugate to the first optical image made
incident into the first imaging unit.
[0013] In the image capturing apparatus, the optical path
difference producing member is disposed on the second optical path.
Thereby, at the first imaging region and the second imaging region
of the second imaging unit, it is possible to image respectively an
optical image which is focused at the front of an optical image
made incident into the first imaging unit (front focus) and an
optical image which is focused at the rear thereof (rear focus).
The image capturing apparatus is able to make a difference in
optical path length without dividing light on the second optical
path for focus control. Therefore, an amount of light at the second
optical path necessary for obtaining information on a focus
position can be suppressed to secure an amount of light on image
pickup at the first imaging unit. Further, in the image capturing
apparatus, the first imaging region and the second imaging region
on the imaging area of the second imaging unit are positioned on
the front side of the imaging area in the scanning direction of the
sample with respect to the region into which an optical image is
made incident which is conjugate to the first optical image made
incident into the first imaging unit. It is, thereby, possible to
obtain in advance a deviation direction of a focus position by a
simple constitution.
[0014] Still further, it is preferable that the optical path
difference producing member is a flat plate member which is
disposed so as to overlap at least on a part of the imaging area
and that the region control unit sets the first imaging region and
the second imaging region respectively to give a region which will
overlap on the flat plate member and a region which will not
overlap on the flat plate member in order to avoid a shadow of the
second optical image by an edge part of the flat plate member. In
this case, use of the flat plate member enables the optical path
difference producing member to be simple in configuration. Further,
the edge part of the flat plate member forms the shadow of the
second optical image at the imaging area of the second imaging
device. Therefore, the first imaging region and the second imaging
region are set so as to avoid the shadow, thus making it possible
to secure accurate control of the focus position.
[0015] It is also preferable that the optical path difference
producing member is a member having a part which undergoes a
continuous change in thickness along an in-plane direction of the
imaging area and that the region control unit sets the first
imaging region and the second imaging region so as to overlap on
the part of the optical path difference producing member which is
different in thickness. In this case, adjustment of a position of
the first imaging region and that of the second imaging region
makes it possible to adjust freely an interval between the front
focus and the rear focus. Thereby, it is possible to detect a focus
position of the sample at high accuracy.
[0016] It is also preferable that the image capturing apparatus is
provided with an objective lens which faces to the sample and an
objective lens control unit which controls the position of the
objective lens relatively with respect to the sample based on
control by the focus control unit, in which the objective lens
control unit will not actuate the objective lens during analysis of
the focus position which is being performed by the focus control
unit and will allow the objective lens to move with respect to the
sample in one direction during analysis of the focus position which
is not being performed by the focus control unit. In this case,
since no change in positional relationship will take place between
the objective lens and the sample during analysis of the focus
position, it is possible to secure analysis accuracy of the focus
position.
[0017] It is also preferable that the region control unit sets the
position of the first imaging region and the position of the second
imaging region in such a manner that an interval between the region
into which an optical image is made incident which is conjugate to
the first optical image made incident into the first imaging device
and the first imaging region is different from an interval between
the region into which an optical image is made incident which is
conjugate to the first optical image made incident into the first
imaging device and the second imaging region. It is, thereby,
possible to secure sufficiently exposure time at the first imaging
region and the second imaging region.
[0018] It is also preferable that the region control unit sets
waiting time from image pickup at the first imaging region to image
pickup at the second imaging region based on a scanning speed of
the stage and an interval between the first imaging region and the
second imaging region. Thereby, since light from the same position
of the sample is made incident into the first imaging region and
the second imaging region, it is possible to control the focus
position at high accuracy.
[0019] Further, the focusing method of the image capturing
apparatus in the present invention is a focusing method of an image
capturing apparatus which is characterized in having a stage in
which a sample is placed, a stage control unit which scans the
stage at a predetermined speed, a light source which radiates light
to the sample, a light guiding optical system including a light
dividing unit which divides an optical image of the sample into a
first optical path for capturing an image and a second optical path
for focus control, a first imaging unit which captures a first
image by a first optical image divided into the first optical path,
a second imaging unit which is capable of capturing a
two-dimensional image of a second image by a second optical image
divided into the second optical path, and a focus control unit
which analyzes the second image to control a focus position of
image pickup by the first imaging unit based on the analysis
result, in which a first imaging region and a second imaging region
for capturing a partial image of the second optical image is
installed on an imaging area of the second imaging unit, an optical
path difference producing member which gives an optical path
difference to the second optical image along an in-plane direction
of the imaging area is disposed on the second optical path, and a
region control unit is used to set the first imaging region and the
second imaging region so as to be positioned on the front side of
the imaging area in a scanning direction of the sample with respect
to a region into which an optical image is made incident which is
conjugate to the first optical image made incident into the first
imaging unit.
[0020] In the focusing method of the image capturing apparatus, the
optical path difference producing member is disposed on the second
optical path. Thereby, at the first imaging region and the second
imaging region of the second imaging unit, it is possible to image
respectively an optical image which is focused at the front of an
optical image made incident into the first imaging unit (front
focus) and an optical image which is focused at the rear thereof
(rear focus). In the focusing method, it is possible to make a
difference in optical path length without dividing light on the
second optical path for focus control. Therefore, an amount of
light at the second optical path necessary for obtaining
information on a focus position can be suppressed to secure an
amount of light on image pickup by the first imaging unit. Further,
in the focusing method, the first imaging region and the second
imaging region on the imaging area of the second imaging unit are
positioned on the front side of the imaging area in the scanning
direction of the sample with respect to the region into which an
optical image is made incident which is conjugate to the first
optical image made incident into the first imaging unit. Thereby,
it is possible to obtain in advance a deviation direction of a
focus position by a simple constitution.
[0021] It is also preferable that as the optical path difference
producing member, there is used a flat plate member which is
disposed so as to overlap at least on a part of the imaging area
and in order to avoid a shadow of the second optical image by an
edge part of the flat plate member, the first imaging region and
the second imaging region are set by the region control unit
respectively so as to give a region which will overlap on the flat
plate member and a region which will not overlap on the flat plate
member. In this case, use of the flat plate member enables the
optical path difference producing member to be made simple in
configuration. Further, the edge part of the flat plate member
forms the shadow of the second optical image at an imaging area of
the second imaging device. Therefore, the first imaging region and
the second imaging region are set so as to avoid the shadow, thus
making it possible to secure accurate control of the focus
position.
[0022] It is also preferable that as the optical path difference
producing member, there is used a member which has a part
undergoing a continuous change in thickness along an in-plane
direction of the imaging area and that the first imaging region and
the second imaging region are set by the region control unit so as
to overlap on the part of the optical path difference producing
member which is different in thickness. In this case, adjustment of
a position of the first imaging region and that of the second
imaging region makes it possible to freely adjust an interval
between the front focus and the rear focus. It is, thereby,
possible to detect a focus position of the sample at high
accuracy.
[0023] It is also preferable that the image capturing apparatus is
provided with an objective lens which faces to a sample and an
objective lens control unit which controls a position of the
objective lens relatively with respect to the sample based on
control by the focus control unit, in which the objective lens
control unit will not actuate the objective lens during analysis of
the focus position which is being performed by the focus control
unit and will allow the objective lens to move with respect to the
sample in one direction during analysis of the focus position which
is not being performed by the focus control unit. In this case,
since no change in positional relationship will take place between
the objective lens and the sample during analysis of the focus
position, it is possible to secure analysis accuracy of the focus
position.
[0024] It is also preferable that the region control unit is
characterized by setting the position of the first imaging region
and the position of the second imaging region in such a manner that
an interval between the region into which an optical image is made
incident which is conjugate to the first optical image made
incident into the first imaging device and the first imaging region
is different from an interval between the region into which an
optical image is made incident which is conjugate to the first
optical image made incident into the first imaging device and the
second imaging region. It is, thereby, possible to sufficiently
secure exposure time at the first imaging region and the second
imaging region.
[0025] It is still also preferable that the region control unit is
used to set waiting time from image pickup at the first imaging
region to image pickup at the second imaging region based on a
scanning speed of the stage and an interval between the first
imaging region and the second imaging region. Thereby, since light
from the same position of the sample is made incident into the
first imaging region and the second imaging region, it is possible
to control the focus position at high accuracy.
Advantageous Effects of Invention
[0026] The present invention is able to obtain in advance a
deviation direction of a focus position by a simple constitution
and also to detect the focus position of the sample at high
accuracy.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a drawing which shows one embodiment of a macro
image capturing device which constitutes an image capturing
apparatus of the present invention.
[0028] FIG. 2 is a drawing which shows one embodiment of a micro
image capturing device which constitutes the image capturing
apparatus of the present invention.
[0029] FIG. 3 is a block diagram which shows functional components
of the image capturing apparatus.
[0030] FIG. 4 is a drawing which shows an analysis result of a
contrast value where a distance to the surface of a sample is in
agreement with the focal length of an objective lens.
[0031] FIG. 5 is a drawing which shows an analysis result of a
contrast value where a distance to the surface of the sample is
longer than the focal length of the objective lens.
[0032] FIG. 6 is a drawing which shows an analysis result of a
contrast value where a distance to the surface of the sample is
shorter than the focal length of the objective lens.
[0033] FIG. 7 is a drawing which shows one example of an optical
path difference producing member and a second imaging device.
[0034] FIG. 8 is a drawing which shows another example of the
optical path difference producing member and the second imaging
device.
[0035] FIG. 9 is a drawing which shows still another example of the
optical path difference producing member and the second imaging
device.
[0036] FIG. 10 is a drawing which shows still another example of
the optical path difference producing member and the second imaging
device (forward direction).
[0037] FIG. 11 is a drawing which shows still another example of
the optical path difference producing member and the second imaging
device (reverse direction).
[0038] FIG. 12 is a drawing which shows still another example of
the optical path difference producing member and the second imaging
device (forward direction).
[0039] FIG. 13 is a drawing which shows still another example of
the optical path difference producing member and the second imaging
device (reverse direction).
[0040] FIG. 14 is a drawing which shows a modified example of the
optical path difference producing member.
[0041] FIG. 15 is a drawing which shows a relationship of the
distance between the objective lens and the surface of the sample
with respect to scanning time of a stage.
[0042] FIG. 16 is a drawing which shows control of a scanning
direction of the stage by a stage control portion.
[0043] FIG. 17 is a drawing which shows control of a scanning speed
of the stage by the stage control portion.
[0044] FIG. 18 is a flow chart which shows motions of the image
capturing apparatus.
DESCRIPTION OF EMBODIMENTS
[0045] Hereinafter, a description will be given in detail of
preferred embodiments of the image capturing apparatus and the
focusing method of the image capturing apparatus in the present
invention with reference to drawings.
[0046] FIG. 1 is a drawing which shows one embodiment of the macro
image capturing device which constitutes the image capturing
apparatus of the present invention. FIG. 2 is a drawing which shows
one embodiment of the micro image capturing device which
constitutes the image capturing apparatus of the present invention.
As shown in FIG. 1 and FIG. 2, an image capturing apparatus M is
constituted with a macro image capturing device M1 for capturing a
macro image of a sample S and a micro image capturing device M2 for
capturing a micro image of the sample S. The image capturing
apparatus M is an apparatus which sets, for example, a plurality of
line-shaped divided regions 40 with respect to the macro image
captured by the macro image capturing device M1 (refer to FIG. 9)
and produces a virtual micro image by capturing and synthesizing
each of the divided regions 40 by the micro image capturing device
M2 at a high magnification.
[0047] As shown in FIG. 1, the macro image capturing device M1 is
provided with a stage 1 which supports sample S. The stage 1 is an
XY stage which is actuated in a horizontal direction by a motor or
an actuator such as a stepping motor (pulse motor) or a piezo
actuator, for example. The sample S which is observed by using the
image capturing apparatus M is, for example, a biological sample
such as cells and placed on the stage 1 in a state of being sealed
on a slide glass. The stage 1 is actuated inside the XY plane, by
which an imaging position with respect to the sample S is allowed
to move. Further, the stage 1 is able to move back and forth
between the macro image capturing device M1 and the micro image
capturing device M2 and provided with functions to deliver the
sample S between the devices. It is acceptable that the stage 1 is
installed both on the macro image capturing device M1 and on the
micro image capturing device M2.
[0048] A light source 2 which radiates light to the sample S and a
condensing lens 3 which concentrates light from the light source 2
at the sample S are disposed on a bottom of the stage 1. It is
acceptable that the light source 2 is disposed so as to radiate
light obliquely to the sample S. Further, a light guiding optical
system 4 which guides an optical image from the sample S and an
imaging device 5 which images the optical image of the sample S are
disposed on an upper face of the stage 1. The light guiding optical
system 4 is provided with an image forming lens 6 which forms the
optical image from the sample S at an imaging area of the imaging
device 5. Still further, the imaging device 5 is an area sensor
which is capable of capturing, for example, a two-dimensional
image. The imaging device 5 captures an entire image of the optical
image of the sample S made incident into the imaging area via the
light guiding optical system 4 and is housed at a virtual micro
image housing portion 39 to be described later.
[0049] As shown in FIG. 2, the micro image capturing device M2 is
provided on the bottom of the stage 1 with a light source 12 and a
condensing lens 13, as with the macro image capturing device M1.
Further, a light guiding optical system 14 which guides an optical
image from the sample S is disposed on the upper face of the stage
1. The optical system which radiates light from the light source 12
to the samples may include an excitation light radiating optical
system which radiates excitation light to the sample S and a
dark-field illuminating optical system which captures a dark-field
image of the sample S.
[0050] The light guiding optical system 4 is provided with an
objective lens 15 disposed so as to face to the sample S and a beam
splitter (light dividing unit) 16 disposed at a rear stage of the
objective lens 15. The objective lens 15 is provided with a motor
and an actuator such as a stepping motor (pulse motor) and a piezo
actuator for actuating the objective lens 15 in a Z direction
orthogonal to a face on which the stage 1 is placed. A position of
the objective lens 15 in the Z direction is changed by these
actuation units, thus making it possible to adjust a focus position
of image pickup when an image of the sample S is captured. It is
acceptable that the focus position is adjusted by changing a
position of the stage 1 in the Z direction or by changing positions
of both the objective lens 15 and the stage 1 in the Z
direction.
[0051] The beam splitter 16 is a portion which divides an optical
image of the sample S into a first optical path L1 for capturing an
image and a second optical path L2 for focus control. The beam
splitter 16 is disposed at an angle of approximately 45 degrees
with respect to an optical axis from the light source 12. In FIG.
2, an optical path passing through the beam splitter 16 is given as
the first optical path L1, while an optical path reflected at the
beam splitter 16 is given as the second optical path.
[0052] On the first optical path L1, there are disposed an image
forming lens 17 which forms the optical image of the sample S
(first optical image) which has passed through the beam splitter 16
and a first imaging device (first imaging unit) 18 in which an
imaging area is disposed at an image forming position of the image
forming lens 17. The first imaging device 18 is a device which is
capable of capturing a one-dimensional image (first image) by the
first optical image of the sample S, including, for example, a
two-dimension CCD sensor and a line sensor capable of realizing TDI
(time delay integration) actuation. Further, in a method which
captures images of the sample S sequentially, with the stage 1
controlled at a constant speed, the first imaging device 18 may be
a device which is capable of capturing a two-dimensional image such
as a CMOS sensor and a CCD sensor. First images picked up by the
first imaging device 18 are sequentially stored in a temporary
storage memory such as a lane buffer, thereafter, compressed and
output at an image producing portion 38 to be described later.
[0053] On the other hand, on the second optical path L2, there are
disposed a view-field adjusting lens 19 which contracts an optical
image of a sample reflected by the beam splitter 16 (second optical
image) and a second imaging device (second imaging unit) 20.
Further, at a front stage of the second imaging device 20, there is
disposed an optical path difference producing member 21 which gives
an optical path difference to the second optical image. It is
preferable that the view-field adjusting lens 19 is constituted in
such a manner that the second optical image is formed at the second
imaging device 20 in a dimension similar to that of the first
optical image. It is also preferable that the optical path
difference producing member 21 is disposed in such a manner that
the face which faces to the second imaging device 20 is in parallel
with the imaging area (light receiving face) 20a of the imaging
device. Thereby, it is possible to reduce deflection of light by
the face which faces to the second imaging device 20 and also to
secure the amount of light received by the second imaging device
20.
[0054] The second imaging device 20 is a device which is capable of
capturing a two-dimensional image (second image) by the second
optical image of the sample S and includes two dimensional sensors,
for example, a CMOS (complementary metal oxide semiconductor) and a
CCD (charged coupled device).
[0055] The imaging area 20a of the second imaging device 20 is
disposed so as to be substantially in alignment with an XZ plane
which is orthogonal to the second optical path L2. The first
imaging region 22A and the second imaging region 22B for capturing
a partial image of the second optical image is set on the imaging
area 20a (for example, refer to FIG. 7). The first imaging region
22A and the second imaging region 22B are set in a direction
perpendicular to a direction at which the second optical image
moves (scanning direction: Z direction) on the imaging area 20a in
association with scanning of the sample S. The first imaging region
22A and the second imaging region 22B are set, with a predetermined
interval kept, each of which captures a part of the second optical
image in a line shape. Thereby, an optical image at the same region
as that of the first optical image of the sample S captured by the
first imaging device 18 can be captured as the second optical image
at the first imaging region 22A and the second imaging region
22B.
[0056] Thereby, at the second imaging device 20, it is possible to
capture an optical image which is focused at the front of the first
optical image made incident into the first imaging device 18 (front
focus) and an optical image which is focused at the rear thereof
(rear focus) based on the position of the first imaging region 22A
and the position of the second imaging region 22B. A focus
difference between the front focus and the rear focus is dependent
on a difference between a thickness and an index of refraction of
the optical path difference producing member 21 through which the
second optical image made incident into the first imaging region
22A passes and a thickness and an index of refraction of the
optical path difference producing member 21 through which the
second optical image made incident into the second imaging region
22B passes. There will be described later a shape of the optical
path difference producing member 21 and an example in which the
first imaging region 22A and the second imaging region 22B are
disposed on the imaging area 20a.
[0057] FIG. 3 is a block diagram which shows functional components
of the image capturing apparatus. As shown in the diagram, the
image capturing apparatus M is provided with a computer system
having housing portions such as a CPU, a memory, a communication
interface and a hard disk, an operation portion 31 such as a
keyboard, a monitor 32 etc. The functional components of the
control portion 33 include a focus control portion 34, a region
control portion 35, an objective lens control portion 36, a stage
control portion 37, an image producing portion 38 and a virtual
micro image housing portion 39.
[0058] The focus control portion 34 is a portion which analyzes a
second image captured by the second imaging device 20 to control a
focus position of an image picked up by the first imaging device 18
based on the analysis result. More specifically, the focus control
portion 34 first determines a difference between a contrast value
of the image captured at the first imaging region 22A and a
contrast value captured at the second imaging region 22B in the
second imaging device 20.
[0059] Here, as shown in FIG. 4, where a focus position of the
objective lens 15 is in alignment with the surface of the sample S,
an image contrast value of the front focus captured at the first
imaging region 22A is substantially in agreement with an image
contrast value of the rear focus captured at the second imaging
region 22B. Thereby, a difference value between them is almost
zero.
[0060] On the other hand, as shown in FIG. 5, where a distance to
the surface of the sample S is longer than a focal length of the
objective lens 15, an image contrast value of the rear focus
captured at the second imaging region 22B is greater than an image
contrast value of the front focus captured at the first imaging
region 22A. Therefore, a difference value between them is a
positive value. In this case, the focus control portion 34 outputs
instruction information to the objective lens control portion 36 so
as to be actuated in a direction at which the objective lens 15 is
brought closer to the sample S.
[0061] Further, as shown in FIG. 6, where a distance to the surface
of the samples is shorter than a focal length of the objective lens
15, an image contrast value of the rear focus captured at the
second imaging region 22B is smaller than an image contrast value
of the front focus captured at the first imaging region 22A.
Therefore, a difference value between them is a negative value. In
this case, the focus control portion 34 outputs instruction
information to the objective lens control portion 36 so as to be
actuated in a direction at which the objective lens 15 is brought
away from the sample S.
[0062] The region control portion 35 is a portion which controls a
position of the first imaging region 22A and a position of the
second imaging region 22B at the imaging area 20a of the second
imaging device 20. The region control portion 35 sets at first the
first imaging region 22A at a predetermined position based on
operation from the operation portion 31 and releases the setting of
the first imaging region 22A after image pickup at the first
imaging region 22A. Then, the region control portion 35 sets the
second imaging region 22B, with a predetermined interval kept in
the Z direction from the first imaging region 22A (scanning
direction), and releases the setting of the second imaging region
22B after image pickup at the second imaging region 22B.
[0063] At this time, waiting time W from image pickup at the first
imaging region 22A to image pickup at the second imaging region 22B
is set based on an interval d between the first imaging region 22A
and the second imaging region 22B and a scanning velocity v of the
stage 1. For example, where the waiting time W is given as time W1
from the start of image pickup at the first imaging region 22A to
the start of image pickup at the second imaging region 22B, it is
possible to determine the waiting time with reference to a formula
of W1=d/v-e1-st, with consideration given to exposure time e1 of
image pickup at the first imaging region 22A and time st from
release of the setting of the first imaging region 22A to the
setting of the second imaging region 22B.
[0064] Further, where waiting time W is given as waiting time W2
from completion of image pickup at the first imaging region 22A to
start of image pickup at the second imaging region 22B, it is
possible to determine the waiting time by referring to a formula of
W2=d/v-st, with consideration given to time st from release of
setting of the first imaging region 22A to setting of the second
imaging region 22B. Still further, an interval d between the first
imaging region 22A and the second imaging region 22B is set based
on a difference in optical path length given by the optical path
difference producing member 21. However, actually, the interval d
corresponds to a distance of the sample S on a slide glass. Thus,
eventually, it is necessary to convert the interval d to the number
of pixels of the second imaging region 22B. Where a pixel size of
the second imaging device 20 is expressed in terms of AFpsz and
magnification is expressed in terms of AFmag, the number of pixels
dpix corresponding to the interval d can be determined by referring
to a formula of dpix=d/(AFpsz/AFmag).
[0065] Further, in setting the position of the first imaging region
22A and the position of the second imaging region 22B on the
imaging area 20a, the region control portion 35 sets the first
imaging region 22A and the second imaging region 22B so as to be
positioned on the front side (upper side) of the imaging area 20a
in the scanning direction of the sample S with respect to the
region into which an optical image is made incident which is
conjugate to the first optical image made incident into the first
imaging device 18. That is, the region control portion 35 sets the
position of the first imaging region 22A and the position of the
second imaging region 22B so that positions imaged at the first
imaging region 22A and the second imaging region 22B of the second
imaging device 20 on the sample S are on the front side of a
position imaged by the first imaging device 18 on the sample S (a
position to be imaged by the first imaging device 18) (refer to
FIG. 17 (a)).
[0066] The position of the first imaging region 22A and the
position of the second imaging region 22B are set as described
above. Thereby, as shown in FIG. 7, an interval between the region
22C into which an optical image is made incident which is conjugate
to the first optical image made incident into the first imaging
device 18 and the first imaging region 22A is different from an
interval between the region 22C into which an optical image is made
incident which is conjugate to the first optical image made
incident into the first imaging device 18 and the second imaging
region 22B. Therefore, it is possible to sufficiently secure
exposure time at the first imaging region 22A and the second
imaging region 22B.
[0067] The first imaging region 22A and the second imaging region
22B can be set, whenever necessary, depending on a shape of the
optical path difference producing member 21. For example, in an
example shown in FIG. 7, an optical path difference producing
member 21A formed with a flat plate-shaped glass member is disposed
so as to overlap on a lower half region of the imaging area 20a in
the Z direction. On the imaging area 20a, the region 22C into which
an optical image is made incident which is conjugate to the first
optical image made incident into the first imaging device 18 is
positioned substantially at the central part of the lower half
region of the imaging area 20a. The sample S moves in a +Z
direction in a visual field of the imaging area 20a in association
with scanning of the sample S by the stage 1.
[0068] Then, each of the first imaging region 22A and the second
imaging region 22B is set in a -Z direction with respect to the
region 22C. The first imaging region 22A is set at an upper half
region of the imaging area 20a which will not overlap on the
optical path difference producing member 21A. The second imaging
region 22B is set at a lower half region of the imaging area 20a
which will overlap on the optical path difference producing member
21A. There is a fear that an edge part E of the optical path
difference producing member 21A may form a shadow 23 of the second
optical image on the imaging area 20a. Therefore, it is favorable
that the first imaging region 22A and the second imaging region 22B
are set at a position which avoids the shadow 23.
[0069] Further, in an example shown in FIG. 8, an optical path
difference producing member 21B in which a flat plate-shaped glass
member substantially equal in area to the imaging area 20a is
allowed to overlap on a flat plate-shaped glass member
substantially equal in area to the lower half region of the imaging
area 20a is disposed so as to overlap on the imaging area 20a.
Then, each of the first imaging region 22A and the second imaging
region 22B is set in the -Z direction with respect to the region
22C. The first imaging region 22A is set at an upper half region of
the imaging area 20a which overlaps on the optical path difference
producing member 21B by thickness covering one sheet of the glass
member. The second imaging region 22B is set at a lower half region
of the imaging area 20a which overlaps on the optical path
difference producing member 21B by thickness covering two sheets of
the glass member.
[0070] In this case as well, there is a fear that an edge part E of
the optical path difference producing member 21B may form a shadow
23 of the second optical image on the imaging area 20a. Therefore,
it is favorable that the first imaging region 22A and the second
imaging region 22B are set at a position which avoids the shadow
23.
[0071] Further, in an example shown in FIG. 9, an optical path
difference producing member 21C composed of a prism-shaped glass
member which continuously increases in thickness moving towards the
+Z direction is disposed so as to overlap on the imaging area 20a.
Then, the region 22C into which an optical image is made incident
which is conjugate to the first optical image made incident into
the first imaging device 18 is positioned substantially at the
central part of the imaging area 20a. Moreover, the first imaging
region 22A, the second imaging region 22B and the region 22C are
set in this order along the +Z direction.
[0072] In this case, the position of the first imaging region 22A
and the position of the second imaging region 22B are adjusted in
the Z direction. Thereby, it is possible to change the thickness of
the optical path difference producing member 21C through which the
second optical image made incident into the first imaging region
22A passes and the thickness of the optical path difference
producing member 21C through which the second optical image made
incident into the second imaging region 22B passes. Thereby, it is
possible to adjust a focus difference between the front focus and
the rear focus. It is also necessary to take into account a change
in focus difference depending on a difference in index of
refraction inside the optical path difference producing member
21.
[0073] Further, the optical path difference producing member 21 is
disposed so that the thickness thereof is symmetrical in the Z
direction. In this case, even where the sample S is reversed in
scanning direction, the position of the first imaging region 22A
and the position of the second imaging region 22B are changed so as
to be symmetrical with respect to the region 22C. Thereby, the
sample S can be subjected to bi-directional scanning. In examples
shown in FIG. 10 and FIG. 11, an optical path difference producing
member 21D which is also formed in a flat plate shape as shown in
FIG. 7 is disposed so as to be in alignment with the center of the
imaging area 20a in the Z direction. Still further, the region 22C
into which an optical image is made incident which is conjugate to
the first optical image made incident into the first imaging device
18 is positioned so as to be in alignment with the center of the
imaging area 20a in the Z direction.
[0074] Then, as shown in FIG. 10, where the sample S is scanned in
the +Z direction, at an upper half region of the imaging area 20a,
the first imaging region 22A is set at a region which will not
overlap on the optical path difference producing member 21D and the
second imaging region 22B is set at a region which will overlap on
the optical path difference producing member 21D. Further, as shown
in FIG. 11, where the sample S is scanned in the -Z direction, at a
lower half region of the imaging area 20a, the first imaging region
22A is set at a region which will not overlap on the optical path
difference producing member 21D and the second imaging region 22B
is set at a region which will overlap on the optical path
difference producing member 21D.
[0075] Further, in examples shown in FIG. 12 and FIG. 13, an
optical path difference producing member 21E composed of a
prism-shaped glass member which continuously increases in thickness
moving towards the center thereof in the Z direction is disposed so
as to be in alignment with the center of the imaging area 20a in
the Z direction. Still further, the region 22C into which an
optical image is made incident which is conjugate to the first
optical image made incident into the first imaging device 18 is
positioned so as to be in alignment with the center of the imaging
area 20a in the Z direction.
[0076] Then, as shown in FIG. 12, where the sample S is scanned in
the +Z direction, at an upper half region of the imaging area 20a,
the first imaging region 22A and the second imaging region 22B are
set respectively so as to be on the upper side and on the lower
side. Further, as shown in FIG. 13, where the sample S is scanned
in the -Z direction, at a lower half region of the imaging area
20a, the first imaging region 22A and the second imaging region 22B
are set respectively so as to be on the lower side and on the upper
side.
[0077] Where the sample S is subjected to bi-directional scanning,
it is acceptable that the optical path difference producing member
21 includes, for example, as shown in FIG. 14(a), an optical path
difference producing member 21F which has a certain thickness at
the central part thereof in the Z direction and decreases in
thickness moving towards the outside the both ends thereof in the Z
direction. It is also acceptable that, for example, as shown in
FIG. 14(b), an optical path difference producing member 21G
composed of two glass members, each of which has a cross section
formed in a prism-shaped right angled triangle, is disposed so as
to decrease in thickness from both ends of the imaging area 20a to
the center thereof in the Z direction.
[0078] Where the region 22C into which an optical image is made
incident which is conjugate to the first optical image made
incident into the first imaging device 18 is set for its position
on the imaging area 20a, at first, a distance between the stage 1
and the objective lens 15 is fixed to adjust a position of the
stage 1 so that a cross line of a calibration slide is positioned
at the center of a visual field of the first imaging device 18.
Then, the second imaging device 20 is adjusted for the back focus
so that the cross line of the calibration slide may come into the
visual field of the second imaging device 20. Finally, the second
imaging device 20 is adjusted for the position in the in-plane
direction so that the cross line of the calibration slide is
positioned at a desired site of the imaging area 20a of the second
imaging device 20.
[0079] The objective lens control portion 36 is a portion which
controls actuation of the objective lens 15. Upon receiving
instruction information output from the focus control portion 34,
the objective lens control portion 36 actuates the objective lens
15 in the Z direction in accordance with contents of the
instruction information. It is, thereby, possible to adjust a focus
position of the objective lens 15 with respect to the sample S.
[0080] The objective lens control portion 36 will not actuate the
objective lens 15 during analysis of the focus position which is
being performed by the focus control portion 34 and will actuate
the objective lens 15 only in one direction along the Z direction
until start of analysis of a next focus position. FIG. 15 is a
drawing which shows a relationship of the distance between the
objective lens and the surface of the sample with respect to
scanning time of the stage. As shown in the drawing, during
scanning of the sample S, there will take place alternately an
analysis period A of the focus position and an objective lens
actuation period B based on an analysis result thereof.
[0081] The stage control portion 37 is a portion which controls
actuation of the stage 1. More specifically, the stage control
portion 37 allows the stage 1 on which the sample S is placed to
scan at a predetermined speed based on operation from the operation
portion 31. By the scanning of the stage 1, an imaging field of the
sample S moves relatively and sequentially at the first imaging
device 18 and the second imaging device 20. It is acceptable that,
as shown in FIG. 16(a), a scanning direction of the stage 1 is
one-directional scanning in which upon every completion of scanning
of one divided region 40, a position of the stage 1 is returned to
a start position of scanning and then a next divided region 40 is
subjected to scanning in the same direction. It is also acceptable
that as shown in FIG. 16(b), the scanning direction is
bi-directional scanning in which after completion of scanning of
one divided region 40, the stage 1 is allowed to move in a
direction orthogonal to the scanning direction and a next divided
region 40 is subjected to scanning in an opposite direction.
[0082] Although the stage 1 is scanned at a constant speed while
images are captured, actually, immediately, after the start of
scanning, there is a period during which the scanning speed is
unstable due to influences of vibrations of the stage 1 etc. Thus,
as shown in FIG. 17, it is preferable that there is set a scanning
width longer than the divided region 40 and an acceleration period
C for accelerating the stage 1, a stabilization period D for
stabilizing a scanning speed of the stage 1 and a slowing-down
period F for slowing down the stage 1 are allowed to take place
individually when scanning is performed outside the divided region
40. It is, thereby, possible to capture an image in synchronization
with a constant speed period E during which the stage 1 is scanned
at a constant speed. It is acceptable that image pickup is started
during the stabilization period D and a data part obtained during
the stabilization period D is deleted after the image has been
captured. The above-described method is desirable when used for an
imaging device which requires void reading of data.
[0083] The image producing portion 38 is a portion at which an
captured image is synthesized to produce a virtual micro image. The
image producing portion 38 receives sequentially first images
output from the first imaging device 18, that is, images of
individual divided regions 40, synthesizing these images to produce
an entire image of the sample S. Then, based on the thus
synthesized image, prepared is an image, the resolution of which is
lower than that of the synthesized image, and housed in a virtual
micro image housing portion 39 by associating a high resolution
image with a low resolution image. It is acceptable that an image
captured by the macro image capturing device M1 is also associated
at the virtual micro image housing portion 39. It is also
acceptable that the virtual micro image is housed as one image or
plurally divided images.
[0084] Next, a description will be given of motions of the
above-described image capturing apparatus M.
[0085] FIG. 18 is a flow chart which shows motions of the image
capturing apparatus M. As shown in the flow chart, at the image
capturing apparatus M, at first, a macro image of the sample S is
captured by the macro image capturing device M1 (Step S01). The
thus captured macro image is subjected to binarization by using,
for example, a predetermined threshold value and, thereafter,
displayed on a monitor 32. A scope for capturing micro images from
macro images is set by automatic setting based on a predetermined
program or manual setting by an operator (Step S02).
[0086] Then, the sample S is transferred to the micro image
capturing device M2 and focusing conditions are set (Step S03).
Here, as described above, based on a scanning velocity v of the
stage 1 and an interval d between the first imaging region 22A and
the second imaging region 22B, a waiting time W is set up to the
start of image pickup at the second imaging region 22B. It is more
preferable that consideration is given to exposure time e1 of image
pickup at the first imaging region 22A, time st from release of
setting of the first imaging region 22A to setting of the second
imaging region 22B etc.
[0087] After setting of focusing conditions, scanning is started at
the stage 1, and the micro image capturing device M2 is used to
capture a micro image of each of the divided regions 40 of the
sample S (Step S04). In capturing the micro image by the imaging
device 18, an extent that the objective lens 15 deviates from the
sample S is analyzed by the second imaging device 20 at the first
imaging region 22A and the second imaging region 22B based on a
difference between the contrast value of the front focus and the
contrast value of the rear focus, thereby adjusting a position of
the objective lens 15 in real time. After completion of capturing
micro images of all the divided regions 40, the thus captured micro
images are synthesized to produce a virtual micro image (Step
S05).
[0088] As described so far, in the image capturing apparatus M, the
optical path difference producing member 21 is disposed on the
second optical path L2. Thereby, at the first imaging region 22A
and the second imaging region 22B of the second imaging device 20,
it is possible to image respectively an optical image which is
focused at the front of an optical image made incident into the
first imaging device 18 (front focus) and an optical image which is
focused at the rear thereof (rear focus). In the image capturing
apparatus M, it is possible to make a difference in optical path
length without dividing light on the second optical path L2 for
focus control. Therefore, an amount of light at the second optical
path L2 necessary for obtaining information on a focus position can
be decreased to secure sufficiently an amount of light on image
pickup by the first imaging device 18.
[0089] Further, in the image capturing apparatus M, the first
imaging region 22A and the second imaging region 22B on the imaging
area 20a of the second imaging device 20 are positioned on the
front side of the imaging area 20a in the scanning direction of the
sample S with respect to the region 22C into which an optical image
is made incident which is conjugate to the first optical image made
incident into the first imaging device 18. Thereby, results of
image pickup by the second imaging device 20 can be captured before
timing of image pickup by the first imaging device 18. It is, thus,
possible to obtain in advance a deviation direction of a focus
position of the objective lens 15 by a simple constitution.
[0090] Still further, in the image capturing apparatus M, waiting
time W from completion of image pickup at the first imaging region
22A to start of image pickup at the second imaging region 22B is
set based on a scanning velocity v of the stage and an interval d
between the first imaging region 22A and the second imaging region
22B. Therefore, it is possible to sufficiently secure exposure time
at the second imaging device 20 and also to control a focus
position of the objective lens 15 at high accuracy.
[0091] Where, as the optical path difference producing member of
the present embodiment, there is used an optical path difference
producing member 21 composed of a flat plate-shaped glass member,
the optical path difference producing member can be made simple in
constitution. In this case, an edge part E of the flat plate member
forms a shadow 23 of the second optical image on the imaging area
20a of the second imaging device 20. Therefore, the first imaging
region 22A and the second imaging region 22B are set so as to avoid
the shadow 23, making it possible to control the focus position of
the objective lens 15 accurately and reliably.
[0092] Further, where, as the optical path difference producing
member of the present embodiment, there is used an optical path
difference producing member 21 composed of a glass member having a
part changing in thickness along the in-plane direction of the
imaging area 20a of the second imaging device 20, the region
control portion 35 is used to adjust the position of the first
imaging region 22A and the position of the second imaging region
22B. It is, thereby, possible to adjust freely an interval between
the front focus and the rear focus. Thus, for example, where a
plurality of contrast peaks are present in an image picked up by
the second imaging device 20 or where a flat-shaped peak is found,
a focus difference between the front focus and the rear focus can
be adjusted to detect the focus position of the sample S at high
accuracy.
[0093] In the above-described embodiment, there is exemplified an
apparatus for producing a virtual micro image. The image capturing
apparatus of the present invention is, however, applicable to
various types of apparatuses, as long as the apparatuses are those
in which an image is captured by scanning a sample at a
predetermined speed by a stage etc.
REFERENCE SIGNS LIST
[0094] 1 . . . stage, 12 . . . light source, 14 . . . light guiding
optical system, 15 . . . objective lens, 16 . . . beam splitter
(light dividing unit), 18 . . . imaging device (first imaging
unit), 20 . . . imaging device (second imaging unit), 20a . . .
imaging area, 21 (21A to 21G) . . . optical path difference
producing member, 22A . . . first imaging region, 22B . . . second
imaging region, 22C . . . region into which optical image is made
incident which is conjugate to first optical image, 23 . . .
shadow, 34 . . . focus control portion (focus control unit), 35 . .
. region control portion (region control unit), 36 . . . objective
lens control portion (objective lens control unit), E . . . edge
part, L1 . . . first optical path, L2 . . . second optical path, M
. . . image capturing apparatus, M1 . . . macro image capturing
device, M2 . . . micro image capturing device, S . . . sample.
* * * * *